The two just seem very similar and it sort of makes sense in that the villein would want revenge occasionally (kind of like how its always the butler)
Yes, they derive from the same latin root (villa) both originally meaning a person of the serf class. OED defines villain as:
- Originally, a low-born base-minded rustic; a man of ignoble ideas or instincts; in later use, an unprincipled or depraved scoundrel; a man naturally disposed to base or criminal actions, or deeply involved in the commission of disgraceful crimes:
The etymology for villain is given as:
Etymology: Anglo-Norman and Old French vilein, vilain, villain (= Provençal vilan , Italian villano , Spanish villano , Portuguese villão ) popular Latin *villānum , accusative singular of *villānus (see villains adj.),
and for villein:
Etymology: Anglo-Norman villein (vilein , -eyn , vyleyn , etc.), var. villain , etc., villain n. Both types of spelling have been freely employed for this special sense of the word, and the tendency to use the form villein has increased in recent years.